The field of the present invention is in-grade lighting systems.
In-grade lighting systems have an infinite number of applications for both indoor and outdoor illumination. Among long-term design issues of concern here, lamp profile for flexible application, maintenance with continued integrity and cooling are addressed.
For indoor applications, in-grade lighting is often utilized to provide general illumination or accent illumination to interior walls and objects in public spaces where the use of surface mounted or exposed fixtures are subjected to vandalism, or where the placement of available electrical service requires its use.
In outdoor applications, such lighting systems can be used to illuminate and thus enhance the effects of a variety of objects such as flag poles, signs, shrubbery, and other architectural points of interest. Outdoor lighting can also provide general flood lighting to areas for security purposes and spotlighting where desired.
In-grade lighting systems are also used in semi-indoor areas such as parking structures to separate vehicular traffic flow from pedestrian traffic, or in transitional spaces such as the parapets of buildings to illuminate architectural elements which require the lighting sources to be hidden completely from view.
As lighting systems in outdoor applications are subject to a wide variety of conditions, particular attention must be directed to long-term survival. Thermal cycling, moisture, corrosive soils, vehicle and foot traffic, periodic maintenance and the like are particularly problematic for in-grade lighting applications. Further, in-grade lighting is found in hardscape applications which make removal and replacement of in-grade fixtures highly undesirable.
For indoor lighting system applications, the depth of the fixture creates challenges in placing them in areas with limited space between floor and ceiling structures. Generally, eight inches has been determined to be the maximum depth acceptable in such multi-story structures, limiting the variety of lamp types available. The general practice of installing electrical supply wiring after fixture housing installation requires direct access to the junction box. With limited depth requirements, junction boxes traditionally have been small and difficult to seal. Electrical supply wiring is solid wire, making its manipulation into a small junction box after fixture splicing difficult. Routing of the spliced wires out of the junction box to the lamp and ballast assemblies within the fixture is further complicated with the limited space.
In-grade lighting can have the problem of accumulating dirt and debris about the lens. Opening the lighting system for maintenance, such as relamping, can allow that material to become lodged further into the fixture. This can interfere with clearance, fit and sealing. Such changes can later result in spontaneous failure or failure under repeated vehicle or pedestrian loading on the lens. Such problems can be further aggravated by the size of the opening required to accommodate a given size lens sight glass. The greater the overall diameter of the lamp at grade, the greater the exposure and force interactions with the fixture.
The foregoing applications and environmental challenges have long been recognized with various design efforts undertaken to satisfactorily meet such challenges. U.S. Reissue Pat. No. 34,709, and U.S. Pat. Nos. 5,198,962; 5,276,583; 5,408,397; 5,486,988; 5,727,873; 6,068,384; all incorporated herein by reference, describe lighting systems and construction that address the challenges of in-grade lighting design. The construction includes improved sealing mechanisms for lighting assemblies, non corroding materials and rugged structures providing improved and reliable indoor and outdoor lighting features.
The heat generated by in-grade lighting systems are of particular concern in the design of indoor applications due to the increased risk of direct contact by the persons occupying the space. This again limits the lamp type availability. These design challenges, particularly in the setting of a sealable lamp housing, are interrelated with changes made to accommodate one challenge often adversely impacting other challenges. Reducing lamp profile adversely impacts variety of lamp offerings, access for relamping and increases heat load. Maintenance, particularly as affecting continued sealing integrity, is adversely impacted by reduction in lamp housing space such as would accompanying reduction in the lamp profile. Cooling needs traditionally are contrary to small housings and are adversely impacted by sealing of the housing which impacts convection. Reduced lamp profile also can adversely impact long demanded features such as the ability to aim the light independently of the housing. Further, where profile is an issue in in-grade applications, flow through cooling which necessarily allows water entry as well, is often inappropriate.
Of long-term concern to those engaged in the design of in-grade lighting fixtures is the provision of lamps for applications in-grade where a highly permanent installation requires long-term reliability, e.g., an in-grade application embedded in a concrete drive or flooring. The longevity of architectural features are typically measured in decades. During that time, even the most reliable fixture will require maintenance to replace the light source. Such maintenance can require lamp replacements, ballast assembly replacements and entry to the junction box and is beyond the control of the designer. As such, accommodating maintenance activity requires virtually foolproof means of reassembly to maintain the sealed integrity of the overall system and the components thereof.
Versatility of application with longevity and repeatable maintenance has long remained a design challenge. Typically components are stacked vertically in in-grade fixtures. This provides easy access through the lens opening for maintenance. Reference is made to the foregoing teachings incorporated herein by reference. With this convention, however, versatility of application is compromised where a relatively deep installation is inappropriate. This is particularly true of the junction box where the wiring is relatively fixed. Components such as lamps, emitters, ballasts and electronic controls can be accessed and even pulled from the housing through the lens opening, given modular construction and ample leads. Rewiring, however, typically requires reentry into the junction box.